Boosting the energy density of highly efficient flexible hybrid supercapacitors via selective integration of hierarchical nanostructured energy materials

Ultrahigh Dispersion of Fe3O4 NPs on Cellulose Nanofibers: Unlocking Superior Visible-Light Photocatalysis

Constructing cost-effective and efficient photocatalysts is crucial for removing harmful contaminants from water sources, ensuring a greener and healthier environment. In this study, highly dispersed magnetic iron oxide (Fe3O4) nanoparticles (NPs) were successfully decorated on cellulose nanofibers (CNFs) by using a simple interfacial strategy. Four hybrid materials (Fe3O4-CNF1, Fe3O4-CNF2, Fe3O4-CNF3, and Fe3O4-CNF4) were systematically synthesized, with Fe3O4-CNF4 identified as the most efficient photocatalyst. The optimized Fe3O4-CNF4 hybrid exhibited a high surface area (54.12 m2/g), enhanced light utilization, and improved charge separation, leading to superior photocatalytic performance. It achieved a 95% removal rate of Rhodamine B (RhB) in 120 min and 99% removal rate of Methylene Blue (MB) in 150 min when exposed to visible irradiation. Moreover, Fe3O4-CNF4 demonstrated excellent recyclability, maintaining high efficiency over five reuse cycles with only ∼7% activity loss. Stability tests under varying catalyst concentrations and pH conditions further confirmed its robustness. Additionally, the primary active species, potential degradation pathways of MB, and the underlying reaction mechanism were systematically analyzed. These findings highlight Fe3O4-CNF4 as a promising visible-light-responsive and reusable photocatalyst for wastewater treatment.

Evaluation and mechanistic analysis of the effect of the addition of alkaline earth metal CaO on Cd solidification enhancement in lightweight aggregate preparation

The volatilization of Cd during the preparation of lightweight aggregates (LWAs) can cause serious damage to the environment, so a method to harmlessly transform Cd during this process is required. In this regard, the alkaline earth metal CaO was added to Cd-containing aggregate raw materials for treatment, and the effect of CaO addition on the properties of LWAs in the presence of chlorine and sulfate was investigated. Kinetic models of the Cd volatilization were established by using the Arrhenius equation to predict the volatilization of Cd at different sintering stages. The results showed that 0.8% wt of CaO under the influence of chlorine can reduce the Cd volatilization rate from 84.9% to 12.64%, corresponding to an increase in the reaction activation energy (E a) from 22.62 to 49.55 kJ mol-1. Additionally, the Cd volatilization rate under the influence of sulfate was reduced from 30% to 8%, with an increase in the E a from 33.25 to 42.62 kJ mol-1. The activation energy increase suggests that the addition of CaO is beneficial because it increases the energy required for Cd volatilization. According to the Cd leaching experiments conducted on the LWAs, it was found that the solidification ratio of Cd was higher than 99.9% for all samples after the addition of CaO. The addition of CaO promotes the formation of CdFe2O4 and anorthite for effective solidification of Cd, thus optimizing the structures of the LWAs. This work may provide a new idea for Cd waste recycling.

Exploring residents' willingness to pay for the research and development of renewable energy: A survey from first-tier cities in China

The research and development (R&D) of renewable energy (RE) is crucial for cost reduction in electricity generation and enhancing power system stability. Compared to traditional fossil fuels, it demands more financial support. To investigate Chinese residents' willingness to pay (WTP) for the R&D of RE and its influencing factors, we conducted a large-scale online survey in four first-tier cities in China in 2023. The research findings indicate that (1) Chinese residents are willing to pay approximately 31.20 yuan (4.34 USD) per month for the R&D of RE. (2) WTP is higher under a mandatory payment model than a voluntary one. (3) Electricity consumption, environmental concern, environmental behavior, willingness to participate, satisfaction with government RE policies, and trust in the government's environmental governance capability significantly influence WTP. (4) Younger, male, and larger household residents exhibit higher WTP. Based on these findings, targeted policy recommendations were proposed.

A Facile Two-Step Hydrothermal Synthesis of Co(OH)2@NiCo2O4 Nanosheet Nanocomposites for Supercapacitor Electrodes

The composites of NiCo₂O₄ with unique structures were substantially investigated as promising electrodes. In this study, the unique structured nanosheets anchored on nickel foam (Ni foam) were prepared under the hydrothermal technique of NiCo₂O₄ and subsequent preparation of Co(OH)₂. The Co(OH)₂@NiCo₂O₄ nanosheet composite has demonstrated higher specific capacitances owing to its excellent specific surface region, enhanced rate properties, and outstanding electrical conductivities. Moreover, the electrochemical properties were analyzed in a three-electrode configuration to study the sample material. The as-designed Co(OH)₂@NiCo₂O₄ nanosheet achieves higher specific capacitances of 1308 F·g^-1 at 0.5 A·g^-1 and notable long cycles with 92.83% capacity retention over 6000 cycles. The Co(OH)₂@NiCo₂O₄ nanosheet electrode exhibits a long life span and high capacitances compared with the NiCo₂O₄ and Co(OH)₂ electrodes, respectively. These outstanding electrochemical properties are mainly because of their porous construction and the synergistic effects between NiCo₂O₄ and Co(OH)₂. Such unique Co(OH)₂@NiCo₂O₄ nanosheets not only display promising applications in renewable storage but also reiterate to scientists of the unlimited potential of high-performance materials.

Hierarchically Developed Ni(OH)2@MgCo2O4 Nanosheet Composites for Boosting Supercapacitor Performance

MgCo₂O₄ nanomaterial is thought to be a promising candidate for renewable energy storage and conversions. Nevertheless, the poor stability performances and small specific areas of transition-metal oxides remain a challenge for supercapacitor (SC) device applications. In this study, sheet-like Ni(OH)₂@MgCo₂O₄ composites were hierarchically developed on nickel foam (NF) using the facile hydrothermal process with calcination technology, under carbonization reactions. The combination of the carbon-amorphous layer and porous Ni(OH)₂ nanoparticles was anticipated to enhance the stability performances and energy kinetics. The Ni(OH)₂@MgCo₂O₄ nanosheet composite achieved a superior specific capacitance of 1287 F g^-1 at a current value of 1 A g^-1, which is higher than that of pure Ni(OH)₂ nanoparticles and MgCo₂O₄ nanoflake samples. At a current density of 5 A g^-1, the Ni(OH)₂@MgCo₂O₄ nanosheet composite delivered an outstanding cycling stability of 85.6%, which it retained over 3500 long cycles with an excellent rate of capacity of 74.5% at 20 A g^-1. These outcomes indicate that such a Ni(OH)₂@MgCo₂O₄ nanosheet composite is a good contender as a novel battery-type electrode material for high-performance SCs.

Carbon Materials as a Conductive Skeleton for Supercapacitor Electrode Applications: A Review

Supercapacitors have become a popular form of energy-storage device in the current energy and environmental landscape, and their performance is heavily reliant on the electrode materials used. Carbon-based electrodes are highly desirable due to their low cost and their abundance in various forms, as well as their ability to easily alter conductivity and surface area. Many studies have been conducted to enhance the performance of carbon-based supercapacitors by utilizing various carbon compounds, including pure carbon nanotubes and multistage carbon nanostructures as electrodes. These studies have examined the characteristics and potential applications of numerous pure carbon nanostructures and scrutinized the use of a wide variety of carbon nanomaterials, such as AC, CNTs, GR, CNCs, and others, to improve capacitance. Ultimately, this study provides a roadmap for producing high-quality supercapacitors using carbon-based electrodes.

Novel Synthesis of Nano Mg(OH)2 by Means of Hydrothermal Method with Different Surfactants

Magnesium hydroxide (MOH) is a widely used inorganic chemical owing to its various properties. Hence, researchers have long studied its synthesis and its unique features. However, the morphological consequences have rarely been studied. Despite having several benefits for synthesizing nanoparticles, the hydrothermal method's main drawbacks are its lengthy processing time and the high cost of raw materials. This research aimed to use more easily obtainable raw materials in a reasonably short time to synthesize MOH in various morphologies. For this purpose, we prepared different samples using the same hydrothermal method to investigate the effects of the precursor and surfactant on the structure, morphology, and size of MOH particles. The results of XRD and FTIR analysis demonstrated that a temperature of 180 °C and a duration of 18 h is not sufficient for MgO as a precursor to obtaining MOH in the hydrothermal method. However, in the presence of different surfactants, MgCl2 resulted in nanoparticles with hexagonal structure and plate, flake, spherical, and disc morphologies.

In Situ Grown Mesoporous Structure of Fe-Dopant@NiCoOX@NF Nanoneedles as an Efficient Supercapacitor Electrode Material

In this study, we designed mixed metal oxides with doping compound nano-constructions as efficient electrode materials for supercapacitors (SCs). We successfully prepared the Fe-dopant with NiCoOx grown on nickel foam (Fe-dopant@NiCoOx@NF) through a simple hydrothermal route with annealing procedures. This method provides an easy route for the preparation of high activity SCs for energy storage. Obtained results revealed that the Fe dopant has successfully assisted NiCoOx lattices. The electrochemical properties were investigated in a three-electrode configuration. As a composite electrode for SC characteristics, the Fe-dopant@NiCoOx@NF exhibits notable electrochemical performances with very high specific capacitances of 1965 F g−1 at the current density of 0.5 A g−1, and even higher at 1296 F g−1 and 30 A g−1, respectively, which indicate eminent and greater potential for SCs. Moreover, the Fe-dopant@NiCoOx@NF nanoneedle composite obtains outstanding cycling performances of 95.9% retention over 4500 long cycles. The improved SC activities of Fe-dopant@NiCoOx@NF nanoneedles might be ascribed to the synergistic reactions of the ternary mixed metals, Fe-dopant, and the ordered nanosheets grown on NF. Thus, the Fe-dopant@NiCoOx@NF nanoneedle composite with unique properties could lead to promising SC performance.

Superhydrophobic and Electrochemical Performance of CF2-Modified g-C3N4/Graphene Composite Film Deposited by PECVD

The physicochemical properties of functional graphene are regulated by compositing with other nano-carbon materials or modifying functional groups on the surface through plasma processes. The functional graphene films with g-C₃N₄ and F-doped groups were produced by controlling the deposition steps and plasma gases via radio frequency plasma-enhanced chemical vapor deposition (RF-PECVD). The first principles calculation and electrochemistry characteristic of the functional graphene films were performed on Materials Studio software and an electrochemical workstation, respectively. It is found that the nanostructures of functional graphene films with g-C₃N₄ and F-doped groups were significantly transformed. The introduction of fluorine atoms led to severe deformation of the g-C₃N₄ nanostructure, which created gaps in the electrostatic potential of the graphene surface and provided channels for electron transport. The surface of the roving fabric substrate covered by pure graphene is hydrophilic with a static contact angle of 79.4°, but the surface is transformed to a hydrophobic state for the g-C₃N₄/graphene film with an increased static contact angle of 131.3° which is further improved to 156.2° for CF₂-modified g-C₃N₄/graphene film exhibiting the stable superhydrophobic property. The resistance of the electron movement of CF₂-modified g-C₃N₄/graphene film was reduced by 2% and 76.7%, respectively, compared with graphene and g-C₃N₄/graphene.

Polypyrrole-Assisted Ag Doping Strategy to Boost Co(OH)2 Nanosheets on Ni Foam as a Novel Electrode for High-Performance Hybrid Supercapacitors

Battery-type electrode materials have attracted much attention as efficient and unique types of materials for hybrid battery supercapacitors due to their multiple redox states and excellent electrical conductivity. Designing composites with high chemical and electrochemical stabilities is beneficial for improving the energy storage capability of battery-type electrode materials. We report on an interfacial engineering strategy to improve the energy storage performance of a Co(OH)2-based battery-type material by constructing polypyrrole-assisted and Ag-doped (Ag-doped@Co(OH)2@polypyrrole) nanosheets (NSs) on a Ni foam using a hydrothermal process that provides richer electroactive sites, efficient charge transportation, and an excellent mechanical stability. Physical characterization results revealed that the subsequent decoration of Ag nanoparticles on Co(OH)2 nanoparticles offered an efficient electrical conductivity as well as a reduced interface adsorption energy of OH- in Co(OH)2 nanoparticles as compared to Co(OH)2@polypyrrole-assisted nanoparticles without Ag particles. The heterogeneous interface of the Ag-doped@Co(OH)2@polypyrrole composite exhibited a high specific capacity of 291.2 mAh g-1 at a current density of 2 A g-1, and showed a good cycling stability after 5000 cycles at 5 A g-1. The specific capacity of the doped electrode was enhanced approximately two-fold compared to that of the pure electrode. Thus, the fabricated Ag-doped@Co(OH)2@polypyrrole nanostructured electrodes can be a potential candidate for fabricating low-cost and high-performance energy storage supercapacitor devices.

Sulfur Nanoparticle-Decorated Nickel Cobalt Sulfide Hetero-Nanostructures with Enhanced Energy Storage for High-Performance Supercapacitors

Transition-metal sulfides exaggerate higher theoretical capacities and were considered a type of prospective nanomaterials for energy storage; their inherent weaker conductivities and lower electrochemical active sites limited the commercial applications of the electrodes. The sheet-like nickel cobalt sulfide nanoparticles with richer sulfur vacancies were fabricated by a two-step hydrothermal technique. The sheet-like nanoparticles self-combination by ultrathin nanoparticles brought active electrodes entirely contacted with the electrolytes, benefiting ion diffusion and charges/discharges. Nevertheless, defect engineers of sulfur vacancy at the atomic level raise the intrinsic conductivities and improve the active sites for energy storage functions. As a result, the gained sulfur-deficient NiCo2S4 nanosheets consist of good specific capacitances of 971 F g-1 at 2 A g-1 and an excellent cycle span, retaining 88.7% of the initial capacitance over 3500 cyclings. Moreover, the values of capacitance results exhibited that the fulfilling characteristic of the sample was a combination of the hydrothermal procedure and the surface capacitances behavior. This novel investigation proposes a new perspective to importantly improve the electrochemical performances of the electrode by the absolute engineering of defects and morphologies in the supercapacitor field.

Two-Dimensional Core-Shell Structure of Cobalt-Doped@MnO2 Nanosheets Grown on Nickel Foam as a Binder-Free Battery-Type Electrode for Supercapacitor Application

Herein, we present an interfacial engineering strategy to construct an efficient hydrothermal approach by in situ growing cobalt-doped@MnO₂ nanocomposite on highly conductive nickel foam (Ni foam) for supercapacitors (SCs). The remarkably high specific surface area of Co dopant provides a larger contacting area for MnO₂. In the meantime, the excellent retentions of the hierarchical phase-based pore architecture of the cobalt-doped surface could beneficially condense the electron transportation pathways. In addition, the nickel foam (Ni foam) nanosheets provide charge-transport channels that lead to the outstanding improved electrochemical activities of cobalt-doped@MnO₂. The unique cobalt-doped@MnO₂ nanocomposite electrode facilitates stable electrochemical architecture, multi-active electrochemical sites, and rapid electro-transports channels; which act as a key factor in enhancing the specific capacitances, stability, and rate capacities. As a result, the cobalt-doped@MnO₂ nanocomposite electrode delivered superior electrochemical activities with a specific capacitance of 337.8 F g^-1 at 0.5 A g^-1; this is greater than pristine MnO₂ (277.9 F g^-1). The results demonstrate a worthy approach for the designing of high-performance SCs by the grouping of the nanostructured dopant material and metal oxides.

Determination of heavy metals in water using an FTO electrode modified with CeO2/rGO nanoribbons prepared by an electrochemical method

The rGO/CeO₂/FTO nanocomposite modified electrode was prepared by an electrochemical method. A simple and highly sensitive electrochemical sensing platform for electrochemical rGO and modified CeO₂ nanoribbons directly on FTO electrodes was developed. Simultaneous determination of Pb²⁺ and Cd²⁺ used the differential pulse anodic stripping voltammetry (DPASV) method. The method was simple to operate, and CeO₂ nanobelts could be obtained simultaneously by electrodeposition and reduction of GO without further processing. This is an environmentally friendly electrochemical method to obtain modified electrodes under mild conditions. The experimental results showed that the linear calibration curves of Pb²⁺ and Cd²⁺ are 1–300 and 0.2–500 μg L⁻¹, respectively. At the same time, no interference from other coexisting metal ions was found during the detection process, which proved that the modified electrode had good stability and repeatability.

The rGO/CeO₂/FTO nanocomposite modified electrode was prepared by an electrochemical method.

Self-Supported Co3O4@Mo-Co3O4 Needle-like Nanosheet Heterostructured Architectures of Battery-Type Electrodes for High-Performance Asymmetric Supercapacitors

Herein, this report uses Co3O4 nanoneedles to decorate Mo-Co3O4 nanosheets over Ni foam, which were fabricated by the hydrothermal route, in order to create a supercapacitor material which is compared with its counterparts. The surface morphology of the developed material was investigated through scanning electron microscopy and the structural properties were evaluated using XRD. The charging storage activities of the electrode materials were evaluated mainly by cyclic voltammetry and galvanostatic charge-discharge investigations. In comparison to binary metal oxides, the specific capacities for the composite Co3O4@Mo-Co3O4 nanosheets and Co3O4 nano-needles were calculated to be 814, and 615 C g−1 at a current density of 1 A g−1, respectively. The electrode of the composite Co3O4@Mo-Co3O4 nanosheets displayed superior stability during 4000 cycles, with a capacity of around 90%. The asymmetric Co3O4@Mo-Co3O4//AC device achieved a maximum specific energy of 51.35 Wh Kg−1 and power density of 790 W kg−1. The Co3O4@Mo-Co3O4//AC device capacity decreased by only 12.1% after 4000 long GCD cycles, which is considerably higher than that of similar electrodes. All these results reveal that the Co3O4@Mo-Co3O4 nanocomposite is a very promising electrode material and a stabled supercapacitor.

Co2P decorated Co3O4 nanocomposites supported on carbon cloth with enhanced electrochemical performance for asymmetric supercapacitors

An effective strategy is demonstrated to promote electrochemical performance by the combination of Co3O4 with Co2P to form a composite electrode.

Electrochemical biosensor based on CuPt alloy NTs-AOE for the ultrasensitive detection of organophosphate pesticides

The electrode material is vital for the performance of the electrochemical biosensor. Lately, many nanomaterials have been developed to improve the sensitivity and detection efficiency of the biosensors. In this work, a kind of one-dimensional nanomaterials, the CuPt alloy nanotubes with an open end (CuPt alloy NTs-AOE), was explored. The nanotubes with an open end can provide a larger electrochemical active surface area and more active sites for the immobilization of enzyme. The CuPt alloy displays excellent conductivity and catalytic activity. In addition, the Cu shows the great affinity to thio-compounds, which can greatly enhance the detection efficiency and sensitivity. As a result, the prepared biosensor demonstrates the wider linear range of 9.98 × 10^-10-9.98 × 10^-5g l^-1for fenitrothion and 9.94 × 10^-11-9.94 × 10^-4g l^-1for dichlorvos (as model OPs ) and with the lower detection limit of 1.84 × 10^-10g l^-1and 6.31 × 10^-12g l^-1(S/N = 3), respectively. Besides, the biosensor has been used to detect the real samples and obtains satisfactory recoveries (95.58%-100.56%).

Thermal Fluxes and Solar Energy Storage in a Massive Brick Wall in Natural Conditions

The thermal state of building elements is a combination of steady and transient states. Changes in temperature and energy streams in the wall of the building in the transient state are particularly intense in its outer layer. The factors causing them are solar radiation, ambient temperature and long-wave radiation. Due to the greater variability of these factors during the summer, the importance of the transient state increases at this time. The study analysed heat transfer in three aspects, temperatures in the outer, middle and inner parts of the wall, heat fluxes between these layers and absorption of solar energy, heat transfer coefficient on the wall exterior was also calculated. The analysis is based on temperature measurements at several depths in the wall and measurements of solar radiation. The subject of research is a solid brick wall. The results show that the characteristics of heat flow in winter and summer for the local climate show distinct differences. In the winter, the maximum temperature difference between the external and internal surface of the wall was 10 °C and in summer, 20 °C. In the winter, the negative flux on the internal surface reached 10 W/m2 and on the external 40 W/m2 and was constant throughout the day. The mean heat transfer coefficient on the exterior surface for winter week was 8 W/(mK). A Nusselt and Biot number for dimensionless convection analysis was calculated. The research contributes to the calculation of the variability of heat or cold demand in a daily period and to learn about the processes of energy storage in the wall using sensible heat.

Resource Assessment of Renewable Energy Systems—A Review

The reduction of greenhouse gas emissions by the energy transition may lead to trade-offs with other impacts on the environment, society, and economy. One challenge is resource use impacts due to increasing demand for high-tech metals and minerals. A review of the current state of the art resource assessment of energy systems was conducted to identify gaps in research and application. Publications covering complete energy systems and supplying a detailed resource assessment were the focus of the evaluation. Overall, 92 publications were identified and categorized by the type of system covered and the applied abiotic resource assessment methods. A total of 78 out of 92 publications covered sub-systems of renewable energy systems, and nine considered complete energy systems and conducted a detailed resource use assessment. Most of the publications in the group “complete energy system and detailed resource assessment” were found in grey literature. Several different aspects were covered to assess resource use. Thirty publications focused on similar aspects including criticality and supply risks, but technology-specific aspects are rarely assessed in the resource assessment of renewable energy systems. Few publications included sector coupling technologies, and among the publications most relevant to the aim of this paper one third did not conduct an indicator-driven assessment.

Facile Fabrication of MnCo2O4/NiO Flower-Like Nanostructure Composites with Improved Energy Storage Capacity for High-Performance Supercapacitors

Over the past few decades, the application of new novel materials in energy storage system has seen excellent development. We report a novel MnCo₂O₄/NiO nanostructure prepared by a simplistic chemical bath deposition method and employed it as a binder free electrode in the supercapacitor. The synergistic attraction from a high density of active sites, better transportation of ion diffusion and super-most electrical transportation, which deliver boost electrochemical activities. X-ray diffraction, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopy have been used to investigate the crystallinity, morphology, and elemental composition of the as-synthesized precursors, respectively. Cyclic voltammetry, galvanostatic charge/discharge, and electron impedance spectroscopy have been employed to investigate the electrochemical properties. The unique nanoparticle structures delivered additional well-organized pathways for the swift mobility of electrons and ions. The as-prepared binder-free MnCo₂O₄/NiO nanocomposite electrode has a high specific capacity of 453.3 C g⁻¹ at 1 Ag⁻¹, and an excellent cycling reliability of 91.89 percent even after 4000 cycles, which are significantly higher than bare MnCo₂O₄ and NiO electrodes. Finally, these results disclose that the as-fabricated MnCo₂O₄/NiO electrode could be a favored-like electrode material holds substantial potential and supreme option for efficient supercapacitor and their energy storage-related applications.

Nanocavity-enriched Co3O4@ZnCo2O4@NC porous nanowires derived from 1D metal coordination polymers for fast Li+ diffusion kinetics and super Li+ storage

Nanocavity-enriched Co3O4@ZnCo2O4@NC porous nanowires have been successfully prepared by a two-step annealing process of one-dimensional (1D) coordination polymer precursors. Such unique nanowires with nanocavity-based porous channels can provide a large specific surface area, which allows fast electron/ion transfer and alleviates the volume expansion caused by strain during the charge/discharge processes. While used as the anode material of lithium-ion batteries (LIBs), Co3O4@ZnCo2O4@NC electrodes exhibit outstanding rate capacity and cycling stability, such as a high reversible capacity of 931 mA h g-1 after 50 cycles at a current density of 0.1 A g-1 and a long-term cycling efficiency of 649 mA h g-1 after 600 cycles at 1 A g-1. This coordination polymer template method lays a solid foundation for the design and preparation of bimetal oxide materials with outstanding electrochemical performance for LIBs.